1. Field of the Invention
The present invention relates to a radio communication system, terminal and packet for multihop communication.
2. Description of the Related Art
A communication system, in which radio communication terminals execute communications, using another or other radio communication terminals as repeater stations, is called a “multihop communication system”. In this system, each radio communication terminal can generate and transmit information, and can also function as a repeater station.
A network that enables communications between first and second radio communication terminals is an ad hoc network. Communications between the first terminal and a repeater terminal, between repeater terminals, and between a repeater terminal and the second terminal are part of the communications executed in the ad hoc network. IBSS (Independent Basic Service Set) stipulated in the IEEE802.11 local area wireless network system (ISO/TEC 8802-11:1999 (E) ANSI/IEEE Std 802.11, 1999 edition) is known as a type of ad hoc network.
Referring to FIG. 1, a description will be given the IEEE802.11 local area wireless network system for enabling communications between terminals. The local area wireless system shown in FIG. 1 is IBSS. In IBSS, a system including only two terminals (e.g. terminals 901 and 902) is a minimum system configuration.
In the ad hoc network in which communications are executed between a plurality of terminals, to transmit data to a destination terminal located in a far place, there are cases where data is directly transmitted to the destination terminal with high communication power, and where another terminal is used as a repeater station via which data is transmitted to the destination terminal. The latter case is multihop communication.
In general, when terminal stations are used as repeater stations and multihop communications are executed via the terminal stations, using IBSS, four addresses are necessary, i.e., an address assigned to a destination repeater station to which a data packet is transmitted directly, an address assigned to an originating repeater station from which the data packet is transmitted directly, an address assigned to the final destination terminal to which the data packed is transmitted, and an address assigned to a sending source terminal by which the packet data is generated.
However, in the conventional IBSS shown in FIG. 1, only three address fields are used, and hence all the above-mentioned four addresses cannot be designated.
Accordingly, in a conventional radio communication terminal, address control concerning IBSS multihop communications cannot be executed using the MAC (Media Access Control) layer level, and hence a level higher than the MAC level must be used to execute the address control.